This invention relates to a bottom dump trailer and particularly to an arrangement for controlling the amount of movement of the doors of a bottom dump trailer for adjustment of the opening between the doors.
Bottom dump trailers are well known and widely used for transportation of gravel and other pourable solids. The trailer generally comprises a frame having ground wheels on the frame for transportation of the frame across the ground. A hopper is mounted on the frame with converging side walls which extend inwardly and downwardly to an open bottom of the hopper through which the pourable material can be dumped. Across the bottom on the outside is provided a pair of clam-shell type doors which pivot about respective axis which are parallel and arranged above the opening so that in a closed position the doors abutt at a central line of contact below the open bottom. A hydraulic cylinder is generally provided together with a control linkage which operates to move the doors simultaneously outwardly from the closed position so that the doors pivot outwardly and upwardly around the bottom edge of the hopper to define an opening between the doors through which the material can be dumped.
It is necessary in a device of this type to be able to adjust the size of the opening. Generally the hydraulic cylinder and linkage is arranged so that it simply moves the doors from the closed position to a wide open position at which the doors are halted either by the end of the stroke of the hydraulic system or by an engagement of the door with some part of the frame. It is however necessary in many cases to control this opening to a reduced width so that the dumping of the material takes place in a controlled manner to form a windrow as the trailer is moved forward.
Generally this limitation of the movement is provided simply by a chain which is draped between the two doors and is adjusted in length so that it becomes taut at a required opening. The doors are provided with suitable hooks for receiving the chain and the operator simply adjusts the chain by selecting a particular location on the chain to attach a link of the chain to a hook.
This adjustment system is effectively universally employed on all devices of this type and is generally accepted in the trade. However it is seriously disadvantageous in that it is difficult for the operator to make the adjustment since he must handle the relatively heavy chain while crawling or lying under the doors and since the amount of adjustment is not readily measurable since all the links look effectively identical and the skill of the operator must be used in selecting the required link for attachment to a suitable hook to render the chain taut at the required opening. This may therefore involve some trial and error and is of course highly inconvenient.